Patterns of Diel activity and movements of the American lobster, Homarus americanus, as determined by ultrasonic telemetry

• Main Author: Christian, John R. (John Robert)
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1995
• Subjects: Newfoundland
• Online Access: https://research.library.mun.ca/4206/; https://research.library.mun.ca/4206/1/Christian_JohnR.pdf; https://research.library.mun.ca/4206/3/Christian_JohnR.pdf

The diel activity and nocturnal movements of the American lobster, Homarus americanus, were studied using a fixed hydrophone array tracking system at Broad Cove, Conception Bay, Newfoundland. Twenty lobsters tagged with ultrasonic transmitters were monitored at various times between September, 1987 and August, 1990, providing 291 nights of tracking data of which 246 were complete (i.e. an animal was monitored for the entire period of darkness). Positional information on active lobsters was recorded every two minutes, providing both temporal and spatial information on activity and movements. It was assumed that lagging did not have a pronounced or prolonged effect on the activity or movements of subjects. -- Lobsters were active on 28.5 % of all tracking nights. Time of onset of activity in the initial shelters averaged 1.5 h after sunset while time of onset of movement from them averaged 2.4 h after sunset. Lobsters were active at or within the final shelter an average of 52 min while the average time of cessation of activity at the final shelter was 5.7 h after sunset. The duration of the activity period, which corresponded to the interim between onset of activity at the initial shelter and cessation of activity at the final shelter, ranged from 6 min to 12.8 h with a mean of 4.0 h. Total out-of-shelter time ranged from 4 min to 12 h with a mean of 2.3 h. The out-of-shelter period was characterized by movement or stationary behaviour. Behaviour was considered stationary if the transmitter position remained the same for a minimum of five minutes. Otherwise, the lobster was considered to be moving. Average movement times and out-of-shelter stationary times were 1.3 h and 1.2 h, respectively, while respective ranges were 4 min to 6 h, and 0 to 10.2 h. -- There was also considerable variation within and between individual lobsters with respect to distance moved. Two measures of distance were calculated; the maximum distance (MD) of a lobster from its initial shelter and the approximate total distance (ATD) moved by ...